Terror plan to empty London

Dramatic plans for the mass evacuation of London in the event of a major terrorist attack have been announced by the Government.

The emergency services have drawn up schemes to move tens of thousands of people by road and rail to special camps in the Home Counties.

Transport Secretary Alistair Darling said plans exist to cover every eventuality, including the "very worst".

The details of the evacuation scheme were confirmed today after the capital staged its biggest-ever rehearsal to deal with a terrorist strike on the London Underground. Hundreds of police, firemen and ambulance staff, many in protective clothing, took part in the simulated gas attack.

The long-planned £500,000 exercise was designed using lessons learned from the terrorist attack on the Tokyo tube in 1995, when deadly sarin gas was released, killing 12 people, leaving thousands seriously ill and bringing chaos to the streets of the Japanese capital.

Sixty police cadets posed as victims in the "attack" on Bank station in the City of London yesterday, though several thousand commuters would have been caught up by any real-life incident.

The exercise came as President George Bush told the American people in a televised address that Iraq was now the " central front" in a global war on terrorism - a war which he said would take time and require "sacrifice".

Last week, the head of Scotland Yard Sir John Stevens said a terror attack on the UK was almost inevitable and police were on high alert.

At the weekend, Al Qaeda released an audio tape warning of a devastating attack that would eclipse the horror of 11 September.

The Government's plans for the mass evacuation of London in the event of a chemical, biological or a nuclear strike are believed to include:

Moving the seat of Government from Whitehall to a secure nuclear bunker in the countryside

Evacuating Londoners to "rest and reception" areas in the Home Counties

Re-housing residents long term in the event of a "dirty bomb" being detonated rendering parts of the capital uninhabitable

Changing the law to allow the Treasury, Bank of England and Financial Services Authority to assume control of trading if the City is attacked

Creating a rapid emergency response to a biological attack, putting thousands of police, health workers and army volunteers on standby to halt the spread of infectious diseases such as smallpox.

A chemical attack involving the release of nerve agents sarin or ricin would cause mass panic and could lead to large-scale casualties.

A biological attack using anthrax or smallpox could cause contamination for years but agents such as anthrax are difficult to release into the air.

A nuclear detonation of a so-called a "rucksack nuke" has been discounted, but a dirty bomb - a mix of nuclear material and conventional explosive - is a real fear. Conventional bombs - postal, suicide and in cars - are easier to produce and plant.

Anti-terrorist experts believe an airline hijack is still a major concern after 11 September.

There are also fears that terrorists could use anti-air missiles to bring down a civilian airliner.

Other obvious "post card" targets would be Big Ben, Buckingham Palace, Tower Bridge and Canary Wharf and police have deployed extra patrols around these sites.

An attack on the Tube is also a major fear since it would spread fear into millions even if the numbers of casualties were small.

Dozens of groups and services have been involved in planning for a major response to a terror attack.

Hospitals and public health bodies have devised emergency plans to deal with anthrax, plague, botulism and smallpox.